WaveForms is a free to use spline / path editor for Phaser.
You can buy the complete source code to WaveForms:
The full source code to the WaveForms Path Editor
- Easily Add and Remove points on the path
- Toggle Grid Snapping
- Keyboard Short-cuts for all functions
- Edit 8 paths at once
- Export as JSON data
With the source you can run WaveForms locally and disable the splash screen. You're then free to add whatever additional features you'd like: tweak the export code, merge it into your own tools, adjust the grid or game size or whatever you require.